The present invention relates generally to the cooling of internal combustion engines, and more particularly to the control of the operating temperature of a locomotive engine.
The apparatus and control schemes developed for the cooling of the engines of modern locomotives, such as those provided by the assignee of the present invention, have become very sophisticated and capable of maintaining the engines within a narrow operating temperature range in order to assure optimal performance. A locomotive must be capable of operating efficiently under a wide range of operating conditions, including winter and summer ambient temperatures, idle to full load power requirements, and cold start to long-term power operations. The cooling system of an internal combustion engine not only protects the engine from overheating, but may also affect the efficiency of operation and the emissions generated by the engine. The demand for higher efficiencies, lower emissions, and broader allowable operating ranges has stimulated numerous advances in the art of cooling systems. For example, U.S. Pat. No. 5,415,147 dated May 16, 1995, issued to Nagle et al., assigned to the assignee of the present invention and incorporated by reference herein, teaches a split temperature regulating system and method for turbo-charged internal combustion engines such as used on locomotives. The control scheme of that patent provides for the independent control of the temperature of the engine coolant and the incoming combustion air, thereby, providing optimal engine mechanical and combustion temperatures under a diverse range of operating conditions. It is also known to protect a locomotive engine by limiting its maximum speed and power output when the temperature of the lubricating oil flowing out of the engine is below a predetermined value. See for example, U.S. Pat. No. 4,592,323, dated Jun. 3, 1986, issued to Vest, assigned to the assignee of the present invention and incorporated by reference herein. U.S. Pat. No. 4,592,323, dated Jun. 3, 1986, issued to Vest, assigned to the assignee of the present invention and incorporated by reference herein.
One of the most extreme operating conditions encountered by a locomotive is operating through a tunnel. The temperature inside a tunnel can often significantly exceed the ambient temperature outside the tunnel. Furthermore, because of the limited air volume surrounding the locomotive inside a tunnel, the cooling air passing through the radiators may contain a significant amount of recycled hot air. As a result, it is not uncommon for the temperature of the engine and cooling system of a locomotive to become very high as the train passes through a tunnel. Once an overheated locomotive exits a tunnel, the cooling system will be operating in a maximum cool down mode, with all radiators, fans, shutters, valves or other such devices being in position to remove a maximum amount of heat from the engine. It has been found that, on rare occasion, the engine of a locomotive having exited a tunnel will experience some internal binding, thereby causing a reduction in the power output of the engine and an increase in the wear of parts within the engine.
Thus, there is a particular need for a cooling system for a locomotive that is capable of preventing any incident of binding in an engine resulting from operation of the locomotive through a tunnel. There is a further need for a cooling system for a locomotive that provides improved protection for the engine over a wider range of operating conditions.
Described herein is an improved method of controlling the operating temperature of the engine of a locomotive, the locomotive having a coolant system for transferring heat from the engine to the ambient air and having an engine lube oil system cooled by the coolant system. The method described herein includes the step of controlling the temperature of coolant flowing into the engine in response to the temperature of lube oil flowing out of the engine, such as by limiting the difference between the temperature of the coolant flowing into the engine and the temperature of the lube oil flowing out of the engine to a predetermined maximum value. The improved method may further include the steps of determining a difference between the temperature of lube oil flowing out of the engine and the temperature of coolant flowing into the engine; and reducing the power output of the engine in response to the difference exceeding a predetermined value. The method may further include the step of further reducing the power output of the engine as a function of the length of time that the difference has exceeded the predetermined value.